11.1 Genes are made of DNA

Griffith Experiment

Viral DNA Background

• Virus – a package of nucleic DNA wrapped in a protein shell that must use a host cell to reproduce, they are not considered living organisms

• Bacteriophage – virus that infects bacteria

• There must be something in a virus that allows it to transform bacteria

Hershey Chase Experiment

Question 1 & 2

1. Explain how experiments done by Griffith, Avery & Hershey and Chase supported that genes are made of DNA? [4 points]

2. Identify the parts of DNA and how the double helix is put together (bases)? [4 points]

11.2 Nucleic acids store information in their sequences of

chemical units

DNA Nucleotide

Nucleotides

• Nucleotides are individual units of DNA that compose the whole chain

• Each nucleotide consists of:

a phosphate

a suger (Deoxyribose)

One of four nitrogen base (A,T,C,G)

Nitrogenous Bases

DNA- structures

Rosalind Franklin & Maurice Wilkins

1950’s photographs of the DNA molecule using X-ray crystallography which showed the shape to be a helix

Erwin Chargaff

• 1951, proved that the % of A = T and % of G = C

Watson &Crick

• 1953, used data from the other scientists and built models to finally figure out the exact structure of DNA

• 1962 won the nobel prize in Medicine

11.3 DNA replication is the molecular mechanism of

inheritance

DNA Replication• Enzymes are protein molecules that

catalyze chemical reactions in a cell – usually any protein ending in “ase” is an enzyme

• Helicase- unwinds DNA• DNA Polymerase 3- Adds

complementary nucleotide• DNA Polymerase 1- Checks for error

DNA Replication

11.4 A gene provides the information for making a specific

protein

Beadle and Tatum

• Beadle and Tatum discovered when looking at mutant Neurospora crassa (bread mold)

• Individual gene produces a specific enzyme

• One gene - one polypeptide (combinaiton of amino acids)

DNA & RNA

• Deoxyribose sugar

• A,T,C,G

• Double strand

• Nucleus

• Ribose sugar• A,U,C,G • Uracil pairs with

adenine• Single strand• Nucleus to

cytoplasm

DNA to Protein

Table of Codons

11.5 There are two main steps from genes to proteins

Transcription: Base Pairing of mRNA with DNA

Steps of Transcription

1. DNA double helix unwound and separated by RNA polymerase

2. RNA polymerase adds RNA nucleotides together, making a single strand of mRNA which is complementary to 1 strand of the DNA

Steps of Transcription

3. mRNA is processed (modified) before leaving the nucleus

a. introns (non coding regions) are cut out of the mRNA

b. exons (coding regions) are “spliced” together to form the

final mRNA product

4. Introns are cut out and exons are spliced together to form the final copy of messenger RNA (mRNA)

RNA editing

Transfer RNA (tRNA)

Adding Amino Acids to a

Polypeptide Chain

Steps of Translation

1. mRNA leaves the nucleus and is transported to the ribosome where translation takes place

2. Ribosome holds onto the mRNA, the mRNA codon AUG is located in the P site of the ribosome

3. tRNA carries an amino acid to the P site of the ribosome

4. Another tRNA carries the next amino acid to the A site of the ribosome

Steps of Translation

5. Two amino acids are joined together with a peptide bond

6. tRNA in the P site leaves7. Ribosome moves along the mRNA until the

next codon is located in the A site (the tRNA which was located in the A site

is now in the P site and is holding the peptide chain)

8. tRNA carries the next amino acid to the A site

Steps of Translation

9. New amino acid is joined to the peptide chain (the polypeptide is made of 3 amino acids)

10. tRNA in the P site leaves

11. Process continues until a stop codon appears in the A site of the ribosome

12. Polypeptide is now complete

Rules for translation

1. Codon is a three-base “word” that codes for one amino acid

2. Determine the amino acid coded for by an mRNA codon use the genetic code

3. Genetic code is universal – all species use the same genetic code, the same 20 amino acids are used in all living organisms

Summary of Translation Process

11.6 Mutations can change the meaning of genes

Point vs. Frameshift Mutations

Chromosome Mutations

How mutations affect genes1. A mutation is any change in the nucleotide

sequence of DNA.2.Two categories of mutations

a. Base substitutions (point)– replacement of one nucleotide with another

i. This can change the protein or not change the protein

b. Base insertions or base deletions (frameshift) – addition of an extra nucleotide or subtracting a nucleotide

i. Have more effect on the protein than a substitution

What causes mutations?

1. Mistakes during DNA replication can cause mutations

2. Mutagens – physical or chemical agents that cause mutationsa. Physical mutagens – high energy radiation, X-

rays, Ultraviolet lightb. Chemical mutagens – chemicals that are

similar to DNA bases and cause incorrect base-pairing

Mutations Effects

Body Cells

• Cancers

Gametes

• Birth defects

• Genetic disorders

Ch. 11 Test

• Vocabulary• DNA & RNA structure• Replication, transcription, translation-

content and problems• Scientists & experiments involved• Mutations & mutagens- types and

effects

13.1 Biologists have learned to manipulate DNA

13.2 Biologists can engineer bacteria to make useful products

Plasmids

Restriction Enzymes

Gene Cloning

Genomic Library

Nucleic Acid Probe

13.3 Biologists can genetically engineer plants and animals

Transgenic Plants

13.4 DNA technologies have many applications

PCR Techniques

Gel Electrophoresis

13.5 Control mechanisms switch genes on & off

Regulation of genes

Lac Operon & repressor

Active Genes

Homeotic Genes